Providing Regional Climate Services to British Columbia

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Disentangling the impacts of climate change and human interventions on the hydrology of key Canadian watersheds

Dr. Stephen J. Déry
June 27, 2018 - 3:30pm to 4:30pm

Room 002, University House 1, UVic
2489 Sinclair Rd.
Victoria , BC
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This talk will also be available remotely via BlueJeans video conferencing software.

This presentation will explore climate change and flow regulation impacts on daily and annual river discharge variations and trends into Hudson Bay, the Nechako and Fraser River Basins over the past half-century or so. The first part of the talk will focus on the 3.7 million km2 Hudson Bay drainage basin for which daily observed streamflow data from the Water Survey of Canada, Manitoba Hydro, Ontario Power Generation and Hydro-Québec for 21 rivers are used in the analyses spanning 1960-2016. Decadal hydrographs of the mean and coefficient of variation of daily river discharge are first developed to assess the changing hydrological regimes in both the four highly regulated (La Grande Rivière, Moose, Nelson, and Churchill rivers), and 17 mostly unregulated systems. Then spectral analyses are used to infer the dominant modes of temporal variability on the river discharge input to Hudson Bay from the regulated and unregulated systems. While the unregulated systems exhibit signals of climate change, these remain secondary relative to flow regulation, even at the larger Hudson Bay drainage basin scale.

The second part of the talk will focus on the Fraser River Basin and its major tributary, the Nechako River whose main stem is highly regulated since the construction of the Kenney Dam, the Skins Lake Spillway, and the Nechako Reservoir in the 1950s.  In this part of the talk, we distinguish the relative contribution of flow regulation and climate change on observed streamflow and water temperature trends in the Nechako River Basin including its principal sub-watersheds over 1950-2015. We compare and contrast observed climatic and runoff trends in eight major sub-watersheds (three regulated and five unregulated) and the basin as a whole. Particular attention is given to the impact of the inter-basin diversion of water to the coastal Kemano Powerhouse and Nechako reservoir operations on downstream flows. Furthermore, we use a hybrid model to simulate daily river water temperature as a function of observed air temperature and discharge at different sites within the Nechako River Basin. The results are then placed within the broader context of the Fraser River Basin. The talk will conclude with a discussion on the potential impacts of observed changes on keystone fish species including salmonids and white sturgeon, as well as with a summary of ongoing efforts to better integrate knowledge on the Nechako River Basin.

Stephen Déry is professor in the Environmental Science and Engineering undergraduate program and the Natural Resources and Environmental Studies graduate program at UNBC. His background is in atmospheric science and he has degrees from York and McGill Universities. Stephen also did post-doctoral positions at the Lamont-Doherty Earth Observatory of Columbia University, New York and held a Visiting Research Scientist position at Princeton University in New Jersey. Stephen is investigating the consequences of climate change on the water cycle of northern and alpine regions, including on snow and ice. A major aspect of this research is to develop a better understanding of the water balance in the Fraser River basin based on field studies, remote sensing data and numerical simulations.

Contributing Authors: Catherine Guay, Rachel Hay, Siraj Ul Islam, Kristina Koenig, Matthew MacDonald, Aseem Sharma, and Tricia Stadnyk